Chapter 114- Refrigerants Flashcards
Liquid refrigerants are defined as
Liquids that, atmospheric pressure, have a boiling point considerably lower than that of water
There are six groups of refrigerant
B1, b2, b3, a1, a2, a3
The B group is characterized by its
Toxicity
The A group is characterized by its
Low toxicity
The number determines its
Flammability
A1 is defined as
Non toxic, non flammable
A2 is defined as
Flammable, low toxicity
A3 is defined as
Low toxicity, highly flammable
B1 is defined as
Highly toxic an non flammable
B2 is defined as
Flammable and highly toxic
B3 is defined as
Highly flammable, highly toxic
Ideal refrigerants have these qualities
Low boiling point at atmospheric pressure
Low condensing pressure
An inoffensive odour
A non poisonous nature
Non corrosive action on metals
Nonflammable and non explosive nature when mixed with air
Reasonable price
Thermodynamic properties include
Pressure Temperature Volume Density Enthalpy Entropy
What is the pressure temperature relationship of refrigerants
The saturation temperature of a liquid in a closed vessel can be raised or lowered by raising or lowering the pressure in a vessel.
What are standard conditions of a refrigerant
Standard evaporator temperature of -15 degrees Celsius
Standard condenser temperature of 30 degrees Celsius
Specific volume is defined as
It is necessary to know the specific volume of a refrigerant while it is a liquid or a vapour under conditions required in the refrigerator it’s specific volume is the the change in volume between states
Density is defined
The density of a liquid refrigerant, required to know the size of valves and piping in a refrigerator. Expressed in kg/ meters cubed
Enthalpy is defined as
Sensible heat in a liquid
Sensible heat plus latent heat in a vapour
Refrigerating effect
The effect of heat being taken away from the surroundings so that cooling may take effect, vapour to a gas requires latent heat energy this is what causes the cooling effect in a refrigerator
Physical properties of refrigerants
Miscibility Leakage tendency Odour Toxicity Flammability/ explosiveness Moisture reaction
Miscibility is defined as
The ability of oil to be absorbed into a refrigerant and vice versa is miscibility
Leakage tendency is defined as
The leakage tendency of a liquid may include factors like Operating pressure Viscosity Density Molecular mass of the refrigerant Larger the molecule, the less of a chance it has to escape Fat kids can't run for long
Odour is
What you smell
Idiot
Used to detect is a refrigerant leak is taking place
When a halide torch is us for leak detection what should be done
Provide ample ventilation
Toxicity is defined as
When e posed to a flame the may react and decompose forming highly toxic vapours, or may be highly toxic to begin with
Will fucking kill you
Moisture reaction must be avoided for two reasons
May cause ice to form between valve and valve seat
Could result in corrosion
Sludge forming
Deterioration of the motor insulation
